Lawmakers and activists across the U.S. are expressing outrage after the Department of Homeland Security announced the arrest of a Columbia University demonstrator whose actions were allegedly “aligned to Hamas,” according to the agency.

Immigrations and Customs Enforcement (ICE) agents on Saturday arrested former Columbia University graduate student Mahmoud Khalil, who was in the U.S. legally on a Green Card. President Donald Trump described Khalil as a “radical foreign pro-Hamas student” in a Truth Social post and vowed more arrests to come.

The arrest sparked outrage among campus pro-Palestine group Students for Justice in Palestine (SJP), which vowed protests in response. SJP Chicago called for a Thursday “emergency protest” near a federal building that houses the offices of Sens. Tammy Duckworth, D-Ill., and Richard Durbin, D-Ill.

Stanford University’s SJP chapter also called for a walkout and rally at the school to protest Khalil’s arrest.

Also reacting was Rep. Rashida Tlaib, D-Mich., who signed a letter, along with 13 fellow Democratic colleagues, demanding the Trump administration release Khalil.

“We are horrified by the recent illegal abduction and now indefinite detention of Mahmoud Khalil — a U.S. legal permanent resident — by Department of Homeland Security agents, and we unequivocally demand his immediate release from DHS custody,” the letter reads.

The American Civil Liberties Union (ACLU) called on supporters to send messages to acting ICE Director Todd Lyons demanding Khalil’s release.

“The Trump administration’s detention of Mahmoud Khalil — a lawful permanent resident of the U.S. — for criticizing foreign and U.S. government policies and participating in protest is an extreme and unprecedented attack on the First Amendment,” the ACLU said.

Press Secretary Karoline Leavitt said Tuesday that while some view Khalil as an activist organized campus events in protest of the war in Gaza, President Donald Trump and his administration see him a terrorist sympathizer.

“Mahmoud Khalil was an individual who was given the privilege of coming to this country to study at one of our nation’s finest universities and colleges and he took advantage of that opportunity, of that privilege, by siding with terrorists — Hamas terrorists who killed innocent men, women and children,” Leavitt told reporters. “This is an individual who organized group protests that not only disrupted college campus classes and harassed Jewish-American students and made them feel unsafe on their own college campus, but also distributed pro-Hamas propaganda — flyers with the logo of Hamas. That is the behavior and activity this individual engaged in.”

Columbia University, when reached for comment, referred to several statements related to ICE actions on campus. One communication released Monday by Interim President Katrina Armstrong acknowledged the “challenging time” created by the presence of ICE agents at the school.

“There have been reports of ICE around campus,” the university wrote in another release from Sunday. “Columbia has and will continue to follow the law.”

Campus Reform Reporter Emily Sturge said the Department of Justice should investigate campus activists such as Khalil for ties to foreign adversaries.

“I think something that the Department of Justice does need to look into is how these things are being funded,” Sturge said. “Where the funding for anti-Israel protests is coming from. It is rumored that there could be ties to Iran.”

The arrest follows intervention by the New York Police Department at a pro-Palestine demonstration at Barnard, the all-women’s liberal arts affiliate of Columbia University. Officers arrested nine individuals and charged them with obstructing governmental administration, trespass and disorderly conduct.

Trump last week pulled $400 million in federal funds from Columbia. He argued the move was in response to Columbia’s failure to take action to confront antisemitism on campus.

Editor’s note: Jessica Botelho contributed to this story.

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